The present invention relates to an offset printing machine with a number printing function, and more particularly to an offset printing machine which is capable of selectively effecting a number print.
An offset printing machine with a number printing function is well known in this field. In some of the conventional printing machines with a number printing function, even in the case where no number print is necessary, it is impossible to dismount a number printing unit.
In offset printing machines which are of a detachable type, in the case where number printing is unnecessary, the number printing unit is removed from the printing machine not to effect the number print. In offset printing machines which are not of a detachable type, even in the case where the number pint is unnecessary, the numbering unit must be operated.
However, even in the numbering unit detachable type printing machine, in the case where the numbering unit is to be dismounted from the machine, the removal work is complicated, and when the numbering unit is again mounted on the machine, it takes a long time to mount the numbering unit in the same position. Also, a special holder station is needed for keeping the removed numbering unit. Furthermore, in the non-detachable type printing machine, since the numbering unit is driven irrespective of the necessity of the numbering print, the numbering unit is driven, resulting in a problem such as frictional wear in mechanical components such as rollers and bearings. Also, there is a fear that an unnecessary load would be imposed on the printing machine as a whole due to the driving operation of the numbering unit.